From 38b6be101006d3e7af972999f45d4f1e8250587a Mon Sep 17 00:00:00 2001 From: Vineeth Karumanchi Date: Wed, 2 Sep 2026 15:58:36 +0530 Subject: [PATCH] net: macb: fix NULL pointer dereference on unbind with fixed-link When the device tree describes a fixed-link and has no "mdio" child node, macb_mii_init() returns early without allocating the MDIO bus, leaving bp->mii_bus as NULL. Two cleanup paths then dereference this NULL bus: 1. On driver unbind, macb_remove() unconditionally calls mdiobus_unregister(bp->mii_bus), which oopses: Unable to handle kernel NULL pointer dereference at virtual address 00000000000004a8 pc : mdiobus_unregister+0x14/0xa4 lr : macb_remove+0x38/0xa4 Call trace: mdiobus_unregister+0x14/0xa4 (P) macb_remove+0x38/0xa4 platform_remove+0x20/0x30 device_release_driver_internal+0x1c8/0x224 unbind_store+0xb4/0xbc 2. On the probe error path in macb_probe(), reached when macb_mii_init() has succeeded but a subsequent step fails, the err_out_unregister_mdio label runs the same unconditional cleanup. mdiobus_unregister() and mdiobus_free() do not guard against a NULL bus, so guard the calls in both macb_remove() and the probe error path. Fixes: d0c3601f2c4e ("net: macb: Avoid 20s boot delay by skipping MDIO bus registration for fixed-link PHY") Signed-off-by: Vineeth Karumanchi Reviewed-by: Xuanqiang Luo Reviewed-by: Nicolai Buchwitz Link: https://patch.msgid.link/20260902102836.2019355-1-vineeth.karumanchi@amd.com Signed-off-by: Jakub Kicinski --- drivers/net/ethernet/cadence/macb_main.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c index b1939da4c95a..8469df0d89c3 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -5976,8 +5976,10 @@ static int macb_probe(struct platform_device *pdev) macb_free_tieoff(bp); err_out_unregister_mdio: - mdiobus_unregister(bp->mii_bus); - mdiobus_free(bp->mii_bus); + if (bp->mii_bus) { + mdiobus_unregister(bp->mii_bus); + mdiobus_free(bp->mii_bus); + } err_out_phy_exit: phy_exit(bp->phy); @@ -6006,8 +6008,10 @@ static void macb_remove(struct platform_device *pdev) unregister_netdev(netdev); macb_free_tieoff(bp); phy_exit(bp->phy); - mdiobus_unregister(bp->mii_bus); - mdiobus_free(bp->mii_bus); + if (bp->mii_bus) { + mdiobus_unregister(bp->mii_bus); + mdiobus_free(bp->mii_bus); + } device_set_wakeup_enable(&bp->pdev->dev, 0); cancel_delayed_work_sync(&bp->tx_lpi_work);